Electron beam-controlling apparatus



Dec. 6, 1960 B. R. CLAY 2,963,607

ELECTRON BEAM-CONTROLLING APPARATUS Filed May 4, 1956 F0005 CURRENTJOUAC! 2 Sheets-Sheet 1 INVENTOR. Bun-rm: R- BLHY I 24AM Dec. 6, 1960 B.R. CLA'Y 2,963,607

ELECTRON BEAM-CONTROLLING APPARATUS Filed May 4, 1956 2 Sheets-Sheet 2551mm? RKSULFM/T H50 Fl 0X 1.90 L IIVE'S F 1% 3 IN V EN TOR Bun-rum R-ELHY V i 126 2k AUTO/FIVE) United States Patent ELECTRONBEAM-CONTROLLING APPARATUS Burton R. Clay, Woodbury, N.J., assignor toRadio Corporation of America, acorporation of Delaware Filed May 4,1956, Ser. No. 582,804

9 Claims. (Cl. 313 -77) This invention relates 'to new and improvedapparatus for use in controlling electrons in cathode ray tubes of thetype employed as color television image reproducing devices.Specifically, the invention relates to apparatus adapted for use inconjunction with cathode ray tubes "having a plane of deflection atwhich electrons are subjected to a scanning movement in their transit toa screen unit of the type comprising a mosaic screen and one or moreadjacent grills or masks through which electrons pass in differentangular directions to preselected dot-like or line-like elemental areasof the mosaic.

While the present invention is herein described as applied to a cathoderay tube of the dot-screen variety disclosed inan article by H. B. Law AThree-Gun Shadow-Mask Color Kinescope (October 1951 issue of Proceedingsof the I.R.E.), its applicability is not so limited, since the inventionmay also be employed with other types of cathode ray tubes wherein theangle of approach of an electron beam toward a mosaic screen determinesits point of contact with the screen. I As described in the cited Lawarticle, the particular screen are which is illuminated at any giveninstant in a cathode ray tube of the type in question i s a function'ofthe precise angle at which the electron beam approaches the colorscreen. When such tubes are manufactured in accordance with present-daymass production methods, it is not always possible to maintain thenecessary accuracy in the assembly of the grill or mask and the phosphorscreen. By virtue of such difiiculties, cathode ray tubes which areotherwise satisfactory in structure must be rejected because of colordilution. One cause of color dilution is misalignment of the maskingelectrode about its longitudinal axis with respect to thephosphorscreen. This type of misalignment results in color dilution of thetangential or rotational variety. Radial misalignment of the mask andscreen causes the electrons to strike a point on the screen'radiallydisplaced from their desired point of impingement, and is herein termedradialf color dilution. Color diluarmor the tangential and/or radialvarieties also result from the presence in the paths of thebeamelectrons of stray magnetic fields such, for example, as the earthsmagnetic field.

It is, therefore, a primary object of the present invention to providenew and improved apparatusfor preventing color dilution of the typestemming from rotational and/ or radial misalignment of the tube partsand/or from magnetic fields. I

Previously proposed solutions to the problem ofcolordilution of thetangential and radial varieties have in volved the use of a plurality ofmagnets located around the screen region of the kinescope, each magnetbeing adjustable in strength and direction of intensity. In one sucharrangement, permanent magnets have been disposed with their axes ofrotation oriented radially of the 'kinescope. Here, tangential error,resulting from ainbient magneticfields parallelto'the longitudinalaxisof the tube, is corrected by bucking or cancelling the undesiredfield by an equal but opposite field from the corrective magnet. Aproblem presented by such prior arrangements, however, is that ofmanipulating the magnets about their radial axes for adjustmentpurposes, so that special receiver cabinets permitting access to themagnets have been required in certain instances. y

In accordance with another arrangement, claimed by this inventor incopending application Serial No. 531,705, each magnet is supportedrotatably about an axis which is parallel to the longitudinal axis ofthe tube so that the direction of flux from the magnet may be adjusted,means being additionally provided for effectively 'controlling theintensity of the fields of the permanent magnets. As will be more fullyappreciated, adjustment of the magnets as to strength and polarizationmay be simply accomplished, in such apparatus, from the front of thecabinet in which the kinescope is housed.

The present invention constitutes an improvement over the latter type ofarrangement in that means are additionally provided for effectinggreater control over the direction and intensity of the correctingmagnetic fields. In general, the present invention provides means forsubjecting the electron beams in the region of the screen-unit tosubstantially constant direct current magnetic fields of such intensity,polarity and orientation as to direct the electrons to their normal orintended points impact on the screen. More specifically, a plurality ofpermanent magnets are arranged around the screen region of a kineseop'e,each magnet being supported for rotation about 'an axis parallel to thelongitudinal axis of the tube. Associated with each of the permanentmagnets, in accordance with a specific form of the invention, aretwopairs of pole-formingmember's, the pairs of pole-forming members beingso disposed that, with the associated magnet in a first position, thetwo pairs of pole-forming members serve to produce an elongated magneticfield (measured arcuately of the tube screen) whose flux lines aretransverse oft-he electron beam path whereby to produce a generallyradial deflection of the electrons to correct for radial mispositioningof the electrons. The pole-forming members are so arranged that, whenthe magnet is rotated about 'its axis -from the first-mentionedposition, the two pairs of members serve to produce afield whose fiuxlines are generally parallel to the tubes longitudinal axis, there by tosubject electrons within the field to a tangential rnoyement in adirection dependent upon the orientation of the magnet. By virtue of thenovel configuration of thepole forming members of the invention, leakageflux from the magnetis advantageously'utilized, in that the effectivefield component of suchfi-ux is in-suc-h-direction as to aid the axialflux between the -,pole members.

The invention is described in greaterdetail-inconnection with theaccompanying two sheets of drawings wherein;

M Fig. l is a side elevational view, partly'in section, of 'a three guntri-color kinescope of conventional construction but which isprovided,in accordance witha specific ,form of the invention, with novelelectron beam :path controlling apparatus; v Fig. 2-is a'diagrammaticillustration of a cathode ra'y tube oriented withrespect to certain axesto be described; -Fig. 3is a fragmentary front view, greatly-enlarged,of the screen of the tube of Fig. 1;

Fig. 4 is a perspective view of one of'the r'nagnet and pole-formingassemblies of'Fig. =1;

Fig. 5 is a plan view of the assembly of Fig. 4;

Fig.6 is a front elevational view of the' assemblyof Fig. 5; A v r Fig.7 is a 's'imp1ified tronflelevational *viewdlIus'tratirig 3 one aspectof the operation of the apparatus of Figs. 4-6;

Fig. 8 is a simplified side view of the apparatus of Figs. 4-6illustrating another aspect of its operation;

Fig. 9 illustrates certain magnetic field lines to be described; and

Fig. 10 is a view corresponding to that of Fig. 7 but illustratinganother aspect of the operation of the present apparatus.

Referring to Fig. 1: the color kinescope 10 shown therein comprises anevacuated envelope having a cylindrical neck portion 12 of glass, forexample, which terminates in a flared cone portion 14 whose larger endis closed by a glass face plate 16 through which the color-phosphorscreen 18 of a bi-part target structure or screen-unit 18--20 isvisible. The other element 20, of the screen-unit comprises an aperturedmask. The tube may be of the type disclosed in the above-cited Lawarticle wherein the phosphor screen 18 is of the well-known dot-screenvariety. As shown in the drawing, the phosphor screen is depositeddirectly upon the rear surface of the face plate 16 and the mask 20 iscurved approximately like the curvature of the face plate. Specifically,the screen 18 is provided on its rear surface with a multiplicity ofgroups of red, blue and green phosphor dots, the dots of each groupbeing arranged at the apices of an equilateral triangle.

The mask 20 of the screen unit 1820 comprises a thin metal platecontaining a multiplicity of apertures arranged in the same triangularpattern as the trios of phosphor dots, there being one mask aperture foreach trio of phosphor dots. The aperture mask 20 is supported in spacedrelationship with respect to the screen 18 by any suitable means, notshown. Such a tube is described in detail in an article entitledDevelopment of a 2l-Inch Metal Envelope Color Kinescope by Seelen et al.which appeared in the March 1955 issue of RCA Review.

The cylindrical neck portion 12 of the kinescope 10 houses threeelectron guns 24, 26 and 28, each of which produces an electron beamintended for bombardment of a particular screen color. The guns 24, 26and 28 may be arranged at the apices of an equilateral triangle as shownin the Law article or in any other suitable manner such, for example, asan in-line arrangement. The electron beams produced by the guns areindicated diagrammatically by the dotted lines 30, 32 and 34 and arefocused in a conventional manner by suitable means indicated as anelectromagnetic focus coil 36 energized by currents from a source 38,whereby to provide fine beam-spots at the screen 18. The electron beamsare subjected to the action of substantially perpendicular magneticfields for the scanning, in horizontal and vertical directions, of aconventional rectangular raster at the screen unit. Such scanning fieldsare produced by means of a deflection yoke 40 which may comprise a pairof normally arranged deflection windings disposed about the necl: of thekinescope and energized by suitable sawtooth currents of television lineand field frequencies from the deflection circuits 42. As indicated bythe dotted line 4444', the plane of deflection for the three beams 30,32 and 34 extends transversely through the deflection yoke 40.

In subsequent portions of the instant specification, reference will bemade to the X, Y and Z axes of the kinescope 10. In order to facilitatean understanding of such designations, Fig. 2 illustrates, in simpilfiedform, the kinescope 10 oriented about its several axes X, Y and Z. Itwill be seen from Fig. 2 that the Z-axis coincides with the longitudinalaxis of the tube, while the X and Y-axes are normal to each other and tothe Z-axis.

As has been stated generally supra, one object of the present inventionis that of eliminating the so-called tangential color dilution whichresults from a situation tantamount to that which exists when the shadowmask of a screen unit is rotationally displaced with respect to thephosphor screen (about their common axis). Fig. 3 illustrates a frontview of such a screen unit, showing a typical case of tangentialdilution. It will be understood that the three beams 30, 32 and 34 areintended to converge at the shadow mask 20 and diverge therefrom so thatthe red beam 30 strikes the red-designated phosphor R and the otherbeams 32 and 34 strike the green and blue-designated phosphors G and B,respectively, which phosphor dots are arranged, as explained, at theapices of an equilateral triangle. Assuming that there is somerotational mislocation of the shadow mask 20 and screen 18 or that thereexists a magnetic field in the path of the beams between the shadow maskand phosphor screen unit such that components of the magnetic field areparallel to the Z axis of the tube, color dilution of the tangentialtype will result. Thus, referring to Fig. 3 wherein it is assumed, forpurposes of simplicity of description, that only the red beam 30 is onand that only the red screen dots R are intended to be struck byelectrons, the tangential color dilution is manifest at peripheralregions of the screen such that the red beam spots are not centeredexactly on the red phosphor dots. Rather, the red beam spots are tangentto or overlap and, hence, illuminate peripheral portions of the adjacentblue and green phosphor dots, thus diluting the red light and preventingit from appearing with its proper degree of saturation.

While not illustrated in the drawing, it will be understood that radialcolor dilution, such as may result from a radial misalignment betweenthe shadow mask 20 and screen 18, would be manifested by the beam spotsbeing shifted laterally (i.e., horizontally or vertically) from itsdesired point of impingement, and that the beam spot intended forillumination of red phosphor dot might instead land on an adjacent blueor green dot.

The present invention eliminates or, at least, substantially minimizesboth forms of color dilution through the agency of means for subjectingthe several electron beams to the action of substantially constant(i.e., D.C.) magnetic fields in their travel between the apertured mask20 and the phosphor screen 18. The intensity and polarity of the fieldare chosen so as to divert the electrons from their predeterminedangularly related paths to other angular directions as required todirect them to their intended points of impact upon the phosphor screen18.

Fig. 1 illustrates means, in accordance with a specific form of theinvention, for providing the requisite axial or transverse magneticfield, such means comprising a plurality of permanent magnets 50disposed in circumferentially spaced relation around the tube adjacentto its screen-unit 18-20. The number of magnets thus employed may vary,but the illustrative embodiment shown herein includes six magnets whichmay be equi-spaced about the screen region of the tube, three on eachside of its vertical centerline. The manner in which these magnetsperform their functions of minimizing tangential and radial colordilution will be explained later. At this point, one of the magnets willbe described in detail in cor nection with Fig. 4.

The permanent magnet 50 is illustrated in Fig. 4 as a bar magnetmagnetized along its longitudinal axis and having north and south polesdesignated N and S. A threaded bolt 70 is secured to the magnet 50, asby means of a rivet or other means (not shown) so that it isperpendicular to the magnet. The bolt 70 is slidably received by abushing 74 which is securely held in an aperture located centrally of acup 78. The end of the bolt 70 remote from the magnet 50 is providedwith a screwdriver slot 80. The bushing 74 is slotted throughout aportion of its periphery as at 86. A generally triangular frictionspring 88 which surrounds the bushing communicates with the bolt 70through the slot 86 and engages the bolt. Thus, as will be understood,the spring 88 is in engagement with the threads of the bolt 70, so that,when the bolt is rotated, it will thread its way to- *tion ishereinafter described in greater detail. point, however, certainspecific structural features of ward or away fromthe cup 78.Alternatively, the bolt may be pulled or pushed through the bushing 74along its axis, which movement is permitted by the expansion of thespring 88 as it is cammed outwardly by the threads.

The cup'78 is formed of iron or other magnetic material and is ofinternal diameter sufiicient to receive the magnet 50. Of the assemblythus far described, all of the members with the exception of the magnet50 and cup 78 may be of any suitable non-magnetic material. The cup 78is supported, with respect to the tube, in a manner to be described, sothat the magnet 50 is rotatable about an axis parallel to thelongitudinal axis of the tube and is movable along the axis of the bolt70.

When the magnet is in its extreme retracted position so that it iswithin the cup 78, the cup acts as a shunt therefor, short-circuitingthe'fiux from the magnet so that the field of the magnet outside of thering is substantially zero; on the other hand, when the magnet .50 is inits extended position (as in Fig. 4), the strength of the field producedby the magnet is at its maximum value. 'For positions of the magnetintermediate the two described extreme positions, proportionatelydifferent field strengths may be obtained.

Associated with each of the magnets 50 described thus far is afiux-spreading or pole-forming assembly comprising a plurality ofpole-forming members. One such assembly is illustrated in a perspectiveview in Fig. 4, the magnet 50 and cup 78 being spaced from thepoleforming assembly in the drawing in order that the elements oftheassembly may be more readily seen. The pole-forming assemblycomprises, in accordance with the specific form of the inventionillustrated herein, first and second pairs of pole members 90 and 92having the configuration shown. The pole members 90 have fluxinput'terminals at their adjacent ends in the form of upwardly bent ears 90a,while the pole members 92 terminate at their adjacent ends in downwardlyturned fluxinput terminals or ears 92a. The ears 90a and 92a lie in acommon vertical plane and are secured, as bv means of rivets 94, to abracket member 96. The pole-forming members 90 and 92 are of suitablemagnetic material such as iron while the bracket 96 is formed of anonmagnetic material such as aluminum. As is shown in Figure 4, the ears90a and 92a of the pole members 90, 92, are located in fixed relation toeach other on the bracket 96, the spacing between the pole member earsbeing such that the magnet 50, when oriented in the position shown inFig. 4, can overlie the ears, such that one pole of the magnet (e.g.,the north pole) over ies the earsi92a and the'other pole of the magnetoverlies the ears 90a. When the magnet 50 is rotated through 90, oneofits poles will be adjacent to the right hand c rs 90a and 92a, whileits other pole is adjacent to the left hand poles 90a and 92:1. Thus, inthe first described position of the magnet (i.e.- illustrated position),the pole members 92 will be energized by flux from the north pole of themagnet, while the pole members 90 will be energized with flux from thesouth pole of the magnet, whereby the members 92 serve as north polesand the pole members 90 serve as south poles.

On the other hand, in the second described position of the magnet (i.e.,rotated 90 clockwise from the showing of Fig. 4), the right hand polemembers 90 and 92 will be energized by the north pole of the magnet andthe left hand pole members 90 and 92 will be energized by the south poleof the magnet.

The manner in which the magnet and pole-forming assembly operate inaccordance with the present inven- At this the pole members are to benoted. Figs. 5 and 6 are, respectively, top and front elevational viewsof the assembly of Fig. 4, Fig. 6 being a view in the direction of thearrow A in Fig. 5. As maybe seen in these figures,

the pole members 90 extend rearwardly from the bracket 96 asindicated bytheir portions 90b and then laterally as indicated by the portions 9%,the extremities 900 being bent downwardly. Each of the pole members 92extends downwardly and forward for a portion 92b and terminates in alaterally, outwardly extending portion 92c. It is to be noted that, asemployed herein, rear and rearwardly refers to the direction of the gunportion of the kinescope which the assemblies are associated, whilefront and forwardly refer to the direction away from the gun toward thescreen of the kinescope.

While the manner in which the pole forming assembly is mounted inoperative relationship with respect to the kinescope 10 does not per seform a part of the present invention, one suitable mounting structure isillustrated in Fig. 5 and is herein described in the interest ofcompleteness. Although not shown in its entirety, there may be provideda mask structure in the form of a continuous element of plastic or othersuitable insulating material which surrounds the extreme peripheralportion of the screen end of the tube. At each magnet location, the maskis formed with axial, rearwardly extending cylindrical extensions 100,each such cylindrical extension having a seat 102 for receiving snuglythe cup 78 with which the permanent magnet 51 is associated. The cup 78may be provided with spaced apertures 164 in its front face, whichapertures receive lugs or key portions 106 extending axially rearwardlyfrom the seat 192, whereby the cup 78 is keyed against rotationalmovement by the lugs. The bracket member 96 is secured to thecylindrical extension 100 as by means of screws 108 which fastenoutwardly bent flanges 110 of the bracket member to the face of theextension 100. The bracket 96 thus additionally serves to hold the cup'78 in its seat 102.

The threaded bolt 76) of the magnet is threadedly received within aninternally threaded tubular extension 112 which is within and concentricwith the cylindrical extenson 100. Thus, the slotted end of the bolt 70may be reached by the shank of a screwdriver through the opening 114which extends through to the front of the support 100.

The manner in which the magnet and pole member assemblies serve tocontrol the paths of electrons traveling toward the screen of thekinescope 10 is now described in connection with Figs. 7-10. Fig. 7illustrates diagrammatically one of the magnet and pole memberassemblies and its relation to the peripheral rim portion of thekinescope 10 in the region of its screen. As may be seen from the frontelevational view of the assembly, the pole members conform generally tothe curvature of the kinescope and extend over an appreciable portion ofthe peripheral dimension of the kinescope. The pole members 92, asdescribed in connection with Figs. 4-6, extend forwardly of the polemembers 90 and also encompass an appreciable arcuate portion of thekinescope screen region. The magnet 59 is further illustrated in Fig. 7in a position for controlling radial positioning of the electron beamstraveling toward the screen. That is to s y. the ma' net is rotated inthe plane perpendicular to the 'Z-axis of the tube such that the polesof the magnet lie along a line parallel to a tangent to the tube. Thus,the north pole of a magnet is illustrated as overlying the ears 92a and90a of the left hand pair of the pole members, while the south pole ofthe magnet overlies the ears 92a and 90a of the right hand pair of polemembers. By reason of the orientation of the magnet 50 in Fig. 7, theleft hand pole members 90 and 92 serve as north poles, while the rightband members serve as south poles, the magnetic flux lines beingindicated by the dotted lines and the direction of the flux lines beingindicated by the arrowheads thereon. It will be appreciated, therefore,that the flux lines 120 constitute a magnetic field whose resultantcomponent in a plane of the drawing is as represented by the arrowdesignated resultant field," whereby electrons passing through the fieldare deflected along a radius of the tube screen, as represented by thearrow labeled beam motion, one of the beams being shown in section bythe circle 122.

From the foregoing description of Fig. 7, it will be noted that themagnet and pole-forming assembly of the present invention may be readilyemployed for the correction of radial color error. The direction of suchcorrection may be reversed from that described by rotating the magnet 50through 180 from the position shown in Fig. 7, while the strength of theresultant magnetic field and, therefore, the degree of correction may becontrolled by retraction of the magnet within the cup 78 or extension ofthe magnet from the cup for less or greater correction, respectively.

Figs. 8l0 illustrate the manner in which the magnet and pole-formingassemblies of the present invention may be employed for the correctionof tangential color error or dilution as defined above. Fig. 8 is adiagrammatic side elevation of one of the magnet and pole-formingassemblies shown in operative relation with respect to the kinescope 10.in Fig. 8, the magnet 50 is positioned with its north and south poleslying along a line which is a radius of the screen of the kinescope (theposition shown in Fig. 4). Thus, the front pole members 92 are energizedby the north pole of the magnet and serve as north poles of the magneticsystem while the rear pole members 90 are energized by the south pole ofthe magnet and constitute the south poles of the system. The flux linesof the magnetic field between the pole members 92 and 96.9 are shown bythe dotted lines 126 and are, in general, parallel to the Z-axis of thekinescope. In the position shown, the apparatus is capable of correctingtangential color dilution such as might be produced by an offendingmagnetic field extending in a direction parallel to the Z-axis of thekinescope and thus designated in Fig. 8. As will become more fullyapparent, the apparatus of the present invention serves in two distinctways to correct for such tangential error. Specifically, one way inwhich tangential error is corrected may be understood from the showingof Fig. 8, in that the flux lines 126 between the pole members 92 and 90constitute an axial field which is of the proper direction and whoseintensity may be controlled to neutralize or buck the offending Z axismagnetic field. Viewed otherwise, an electron beam in its deflectedposition as shown by the curved line 128 sees a transverse magneticfield as shown in Fig. 9, so that the beam is deflected laterally ortangentially as indicated by the arrow 130 in Fig. 9.

The second way in which the present apparatus corrects for tangentialerror stems from the fact that a certain amount of leakage flux, shownby the curved lines 132 in Fig. 8, surrounds the magnet 50. This leakageflux is three-dimensional and is further illustrated by the flux lines132a in Fig. 10. With the magnet oriented with its north pole overlyingthe ears of the pole members 92 as in Figs. 8 and 10, there is presentan effective field component which may be termed a quadrature fieldwhich is represented by the arrow 134. This quadrature field componentwill be understood as being radial of the tube, so that an electron beamin the region of the field is moved tangentially as represented by theline 136 (Fig. The direction in which the beam is thus movedtangentially by the quadrature field of the magnet 54} is determined bythe orientation of the magnet.

It is further important to note that, with the specific configuration ofpole members illustrated herein, the quadrature field component 134which is the resultant of the leakage flux of the magnet when alignedalong the radius of the tube is always in such direction as to aid theaxial flux lines (e.g., the flux lines 126 in Figs. 8, 9 and 10). Thus,the direction in which electrons are tangentially deflected by thequadrature component is the same as that in which it is deflected by theaxial component represented by the lines 126. The reason for this aidingelfect may be explained as follows: in order that the magnet may berotatable for adjustment in a plane perpendicular to the Z axis of thekinescope and in order for the pole members to be capable of producingan axially extending field such as that represented by the flux lines126, the two pairs of pole members must converge in a plane or planesparallel to the plane of rotation of the magnet. This requirement, inturn, results in the requirement that the ear portions of one pair ofpole members (i.e., the pole members 92) be located farther out along aradius of the tube than the other pair (i.e., the members The foregoingconditions may be met in either of two ways, namely, with the pair ofpole members whose ear portions are farther from the tube extendingforwardly of the other pair or rearwardly of the other pair.

In order for the quadrature component 134 to aid the axial componentregardless of whether clockwise or counter-clockwise tangential movementof the beams is to be produced in a given case, however, that pair ofpole pieces energized by the upper pole of the magnet (by upper is meantthe pole farther from the tube when the magnet is aligned along a radiusof the tube) must belocated forwardly of the other pair of pole members.That is to say, in the illustrative example shown, the pole members 92are energized by the upper pole of the magnet 50 when it is orientedalong the radius of the tube and these pole members extend forwardly ofthe other pair of pole members (i.e., the members 90). It has been foundthat, unless this last-mentioned condition exists, the quadrature fluxcomponent 134 will buck or be of the opposite sense from the axial flux126. It will be appreciated, however, that the apparatus of the presentinvention affords greater control over tangential error than that whichis available in the absence of the pole-forming members. As in the caseof radial correction described above, the degree of tangentialcorrection may be varied by movement of the magnet along its axes ofrotation toward or away from its cup.

What is claimed is:

1. An adjunct for a cathode ray tube of the type including a plane ofdeflection at which electrons are subjected to a scanning deflection intheir transit along the longitudinal axis of such tube toward a screenunit including a target made up of a plurality of respectively differentelemental areas, said adjunct comprising: a permanent magnet havingnorth and south poles; means for supporting said magnet in the region ofsuch screen unit for rotation in a plane substantially perpendicular tothe longitudinal axis of such tube; and pole-forming members havingflux-input terminals disposed adjacent to said magnet in a planesubstantially perpendicular to said longitudinal axis and includingmeans for directing flux from said magnet selectively in lines generallyparallel to such axis or in lines which are generally tangential to suchscreen unit as determined by the angle of rotation of said rotatablysupported magnet.

2. An adjunct for a cathode ray tube of the type including a plane ofdeflection at which electrons are subjected to a scanning deflection intheir transit along the longitudinal axis of such tube toward a screenunit including a target made up of a plurality of respectively diflerentelemental areas, said adjunct comprising: a permanent magnet havingnorth and south poles; means for supporting said magnet in the region ofsuch screen unit for rotation in a plane substantially perpendicular tothe longituidnal axis of such tube; a member of flux permeable material;means for producing relative movement between said magnet and saidmember for controlling the effective intensity of the field of saidmagnet; and pole-forming members associated with said magnet fordirecting flux from said magnet in lines generally parallel to suchlongitudinal axis, said pole-forming members being arranged to extendover an arcuate portion of such screen unit and having flux-inputterminals disposed adjacent to said magnet in a plane substantiallyperpendicular to said longitudinal axis.

3. An adjunct for a cathode ray tube of the type including a plane ofdeflection at which electrons are subjected to a scanning deflection intheir transit along the longitudinal axis of such tube toward a screenunit including a target made up of a plurality of respectively differentelemental areas, said adjunct comprising: a permanent magnet havingnorth and south poles; means for supporting said magnet in the region ofsuch screen unit for rotation in a plane substantially perpendicular tothe longitudinal axis of such tube; and pole-forming members associatedwith said magnet for directing flux from said magnet in lines which aregenerally tangential to such screen unit, said pole-forming membersextending laterally outwardly on both sides of said magnet and havingflux-input terminals disposed adjacent to said magnet in a planesubstantially perpendicular to said longitudinal axis.

4. An adjunct for a cathode ray tube of the type including a plane ofdeflection at which electrons are subjected to a scanning deflection intheir transit along the longitudinal axis of such tube toward a screenunit including a target made up of a plurality of respectively differentelemental areas, said adjunct comprising: a plurality of permanentmagnets, each of which has a north and south pole; means for supportingsaid magnets around the screen unit of such tube for rotation in a planesubstantially perpendicular to the longitudinal axis of such tube; andpole-forming members associated with each of said magnets for directingits flux along lines generally parallel to such longitudinal axis, saidpoleforming members each having flux-input terminals disposed adjacentto its magnet with the terminals of all said members disposed in acommon plane substantially perpendicular to said longitudinal axis.

5. An adjunct for a cathode ray tube of the type ineluding a plane ofdeflection at which electrons are subjected to a scanning deflection intheir transit along the longitudinal axis of such tube toward a screenunit including a target made up of a plurality of respectively differentelemental areas, said adjunct comprising: a plurality of permanentmagnets, each of which has a north and south pole; means for supportingsaid magnets around the screen unit of such tube for rotation in a planesubstantially perpendicular to the longitudinal axis of such tube; andpole-forming members associated with each of said magnets for directingits flux along lines generally tangential to such screen unit, saidpole-forming members each having flux-input terminals disposed adjacentto its magnet with the terminals of all said members disposed in acommon plane substantially perpendicular to said longitudinal axis.

6. An adjunct for a cathode ray tube of the type in which electrons aresubjected to a scanning deflection in their transit along thelongitudinal axis of such tube toward a screen unit including a targetmade up of a plurality of respectively diflerent elemental areas, saidadjunct comprising: a permanent magnet having north and south poles;means for supporting said magnet in the region of such screen unit forrotation in a plane substantially perpendicular to the longitudinal axisof such tube; first and second pole members, each having a firstextremity located adjacent to said magnet and arranged so that saidfirst extremities are spaced generally along a radius of such screenunit, one of said pole members extending rearwardly of said magnet andthe other of said pole members extending forwardly of said magnet.

7. An adjunct for a cathode ray tube of the type in which electrons aresubjected to a scanning deflection in their transit along thelongitudinal axis of such tube from an electron source toward a screenunit including a target made up of a plurality of respectively differentelemental areas, said adjunct comprising: a permanent magnet havingnorth and south poles; means for supporting said magnet in the region ofsaid screen unit for rotation in a plane substantially perpendicular tothe 1ongitudinal axis of such tube, first and second pole members, eachhaving a first extremity located adjacent to said magnet and arranged sothat said first extremities are spaced generally along a radius in suchscreen unit whereby, when said magnet is oriented with its poles alignedalong a radius of the screen unit, said first pole member is energizedby that pole of the magnet nearer said longitudinal axis and said secondpole member is energized by the other pole of the magnet, said firstpole member extending rearwardly from said magnet toward such electronsource and said second pole member extending forwardly from said magnet.

8. An adjunct for a cathode ray tube of the type in which electrons aresubjected to a scanning deflection in their transit along thelongitudinal axis of such tube from an electron source toward a screenunit including a target made up of a plurality of respectively differentelemental areas, said adjunct comprising: a permanent magnet havingnorth and south poles; means for supporting said magnet in the region ofsuch screen unit for rotation in a plane substantially perpendicular tothe longitudinal axis of such tube; first and second pole members, eachhaving a first extremity located adjacent to said magnet and arranged sothat said first extremities are spaced generally along a radius of suchscreen unit whereby, when said magnet is oriented with its poles alignedalong a radius of the screen unit, said first pole member is energizedby the pole of the magnet nearer said longitudinal axis and said secondpole member is energized by the other pole of said magnet, said firstpole member extending rearwardly toward such electron source andlaterally over an arcuate portion of such screen unit and said secondpole member extending forwardly from said magnet and laterally in thesame direction as the lateral extension of said first pole member.

9. An adjunct for a cathode ray tube of the type in which electrons aresubjected to a scanning deflection in their transit along thelongitudinal axis of such tube from an electron source toward a screenunit, said adjunct comprising: a permanent magnet having north and southpoles; means for supporting said magnet in the region of such screenunit for rotation in a plane substantially perpendicular to thelongitudinal axis of such tube; the pole members of said first andsecond pairs each having a first extremity located adjacent to saidmagnet, each of said first extremities being arranged in a planeparallel to the plane of rotation of said magnet and all convergingtoward the axis of rotation of said magnet such that, when said magnetis oriented with its poles aligned along a radius of such screen unit,the pole members of said first pair are energized by the pole of themagnet nearer the longitudinal axis of such tube and the pole members ofsaid second pair are energized by the other pole of said magnet, thepole members of said first pair extending rearwardly toward suchelectron source and outwardly toward opposite sides of said magnet andthe pole members of said second pair extending forwardly from saidmagnet and to opposite sides thereof,

References Cited in the file of this patent UNITED STATES PATENTS2,258,643 De Gier et al. Oct. 14, 1941 2,513,221 Webb June 27, 19502,541,446 Trott Feb. 13, 1951 2,816,244 Hillegass Dec. 10, 19572,825,835 Heppner Mar. 4, 1958 OTHER REFERENCES R.C.A. Service Data,1954, No. T-13, 1st printing, November 24, 1954. v

